Abstract

The summer 2005 flood of the Saskatchewan River (Cumberland Marshes, east-central Saskatchewan) inundated large areas of floodplain for up to seven weeks, forming prominent new deposits on natural levees along main-stem channels. Measurements of flood-deposit thickness and crest heights of 61 levee pairs show that the thickest deposits occur on the lower pre-flood levee in 80% of the sites, though no clear relationship exists between deposit thickness and magnitude of height difference. Supplemental observations from tank experiments indicate that during near-bankfull flows, temporally and spatially variable deposition and erosion occur on levees due to backwater effects associated with nearby channel bars and irregular rises of the channel bed forced by channel extension. During floods, preferential deposition in lows tends to even out crest heights